Satsumas and upcoming freeze

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All ripe fruit should be harvested from trees prior to a significant freeze event. Temperatures cold enough to damage the tree will also ruin the fruit. It takes temperatures in the mid- to low 20s five to 10 hours to freeze the fruit.

Three factors which are basically involved in determining freeze susceptibility of citrus trees are:

1) The type and age of the citrus. Satsumas are the most cold hardy of the commonly grown citrus species in Louisiana. Kumquats follow with just a slight less amount of cold hardiness. In order from most cold hardy to least cold hardy: satsuma, kumquat, orange, grapefruit, lemon and lime. A citrus tree increases in hardiness as it gets older. Trees with larger, denser canopies deal with the cold better as they trap more heat.

2) Threshold temperatures are approximately 20 degrees for satsumas and kumquats, and about 26 degrees for all other citrus.

3) The duration of the sub-freezing temperature is very significant. If the temperature is below freezing for 24 to 36 hours, damage can usually be expected.

Generally, when freeze injury occurs, damage is inflicted mostly to cell membranes by freezing and thawing. The least cold hardy tissues of citrus trees are new buds, flowers, and small fruit. The more cold hardy part of the tree is the mature wood of major branches and the trunk.

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